1. Field of the Invention
The disclosed embodiments of the present invention relate to audio playback, and more particularly, to a method for synchronizing audio playback of a plurality of digital media renders (DMRs) and related digital media controller and digital audio media render.
2. Description of the Prior Art
An industrial standard of mutual connection and mutual adaption of products of distinct manufacturers for providing digital living to consumers is achieved by the Digital Living Network Alliance (DLNA). The DLNA specification is also employed by a home digital audio and video media playback system including a digital media controller (DMC), a digital media server (DMS), and a plurality of digital media renders (DMRs). However, in a case where the DMRs, the DMS and the DMRs are connected via wireless connections, the DMRs receive audio data from the DMS for audio playback byway of wireless connection. The advantages include simplified wired configuration and enhanced flexibility for future equipment update. However, the disadvantage is that a wireless transmission has poorer stability when compared with a wired transmission. The DMRs may be asynchronous to each other apparently at the initial condition of the playback or during the playback as the system is subject to interference. Even though the wireless connection is stable, the DMRs may be asynchronous to each other gradually due to a slight difference between DMRs' oscillator frequencies. Therefore, how to control and synchronize a plurality of DMRs has become a significant concern in this field.
Regarding the conventional design of synchronization of the DMRs, an absolute timing concept is employed. Specifically, each DMR may have information with absolute timing to comply with. However, many systems, including the DLNA system, do no offer the information about the absolute timing due to simplified system designs. As a result, the conventional synchronization method cannot be employed by these systems. Therefore, there is a need for an innovative design which can synchronize a plurality of DMRs.